This application is based on applications Nos. 225080/1998, 225081/1998 and 52924/1999 filed in Japan, the contents of which is hereby incorporated by reference
1. Field of the Invention
The present invention relates generally to a developing apparatus used for developing an electrostatic latent image formed on an image carrying member in an image forming apparatus such as a copying machine or a printer, and more particularly, to a developing apparatus for conveying a developer held in the surface of the developer carrying member to a developing area opposite to the image carrying member as well as applying an AC voltage to the developer carrying member to perform development, characterized in that the developing characteristics thereof are improved, to obtain an image having a sufficiently image density, and the density of the image can be suitably controlled.
2. Description of the Related Art
In an image forming apparatus such as a copying machine or a printer, various developing apparatuses have been conventionally used for developing an electrostatic latent image formed on an image carrying member.
A developing apparatus shown in FIG. 1 has been known as one of such developing apparatuses.
In the developing apparatus shown in FIG. 1, a magnet member 12 having a plurality of magnetic poles N, S, . . . on the side of the inner periphery of a cylindrical developer carrying member 11 provided opposite to an image carrying member 1 is provided, to mix and agitate a developer 2 containing toners and carriers which are contained in the main body 10 of the apparatus by a developer agitating member 13 and to supply the developer 2 to the developer carrying member 11 by the developer agitating member 13. The developer 2 is held in the surface of the developer carrying member 1 by a magnetic force of the magnet member 12.
The developer carrying member 11 is rotated to convey the developer 2, and the amount of the developer 2 thus conveyed is adjusted by a regulating member 14, to convey the developer 2 in a suitable amount to a developing area opposite to the image carrying member 1 by the developer carrying member 11. A DC voltage is applied to the developer carrying member 11 from a DC power supply 15, and an AC voltage is applied thereto from an AC power supply 16, to exert an electric field which is an overlapping of a DC electric field and an AC electric field on the developing area where the developer carrying member 11 and the image carrying member 1 are opposite to each other. Toners in the developer 2 are supplied to an electrostatic latent image portion formed in the image carrying member 1 from the developer carrying member 11, to perform development.
When the toners in the developer 2 are thus supplied to the electrostatic latent image portion formed in the image carrying member 1 to perform development by applying the DC voltage to the developer carrying member 11 from the DC power supply 15 and applying the AC voltage thereto from the AC power supply 16, the toners in the developer 2 are not suitably supplied in correspondence with a surface potential at the electrostatic latent image portion formed in the image carrying member 1. Accordingly, there are some problems. For example, an image having a sufficient image density cannot be obtained, and the density of a formed image cannot be suitably controlled.